In the United States, the Emergency Alert System (“EAS”) replaced the older Emergency Broadcast System in January 1997. The EAS allows the President of the United States of America, or one of his representatives, to address the Nation during national emergency situations. EAS places the Nation's broadcast and cable industries at the President's disposal for addressing the Nation. The Federal Communications Commission (“FCC”), along with the National Weather Service (“NWS”) and the Federal Emergency Management Agency (“FEMA”), implement EAS.
EAS utilizes Audio Frequency Shift Keying (“AFSK”) to send a data signal on a broadcast station's main audio channel. Weekly tests of the AFSK, and monthly on-air tests for television and radio stations are performed by EAS. The utilization of AFSK allows EAS to send data to unattended stations. The EAS equipment receives a message, interrupts a station's regular programming, sends the alert warning, and then automatically returns the station to normal programming.
There is also a large interest in identifying and/or measuring audience exposure to audio data in order to provide market information to, for instance, advertisers and media distributors, for any purpose for which an estimation of audience receipt or exposure is desired.
One technique utilized for audience measurement involves adding an ancillary code to the audio data for use in producing audience estimates. An encoder is typically utilized by the radio station, broadcast TV station or cable location to insert an inaudible code into the audio spectrum of the media source. These signals are then received and decoded at the audience location to uniquely identify the program signal.
However, when an EAS signal passes through such an encoder, the characteristics of the EAS signal may be modified. The modified EAS signal may not operate properly with the studio broadcast equipment. A typically improper operation could be, for instance, the studio control equipment failing to detect and activate in response to an EAS signal, or the studio control equipment failing to turn off from EAS mode once the EAS broadcast has been completed.
As the EAS is maintained for use in national emergency situations, it is vital that nothing interfere with the EAS broadcast transmission.
However, it is also very important to advertisers and media distributors that they receive comprehensive audience measurement information. Therefore, any interruption in the identification of a program signal that an audience is exposed to should be minimized.
Therefore, what is desired is to provide an encoding system that will not interfere with the effective detection of an EAS code and/or another higher priority code.
It is further desired to provide an encoding system that will minimize any interruption in audience measurement after an EAS code or another higher priority code is detected.
It is further desired to provide an encoding system that will reliably ensure that the audience measurement system will continue to function after the cessation of the EAS code or other higher priority code.